the impact of cpg island on defining transcriptional activation of the mouse l1 retrotransposable elementscpg岛定义的影响转录激活鼠标l1 retrotransposable元素.pdf

The Impact of CpG Island on Defining Transcriptional Activation of the Mouse L1 Retrotransposable Elements 1 2 1 1 1 Sung-Hun Lee , Soo-Young Cho , M. Frances Shannon , Jun Fan , Danny Rangasamy * 1The John Curtin School of Medical Research, Australian National University, Canberra, Australia, 2 Division of Molecular and Life Sciences, Hanyang University, Ansan, Republic of Korea Abstract Background: L1 retrotransposable elements are potent insertional mutagens responsible for the generation of genomic variation and diversification of mammalian genomes, but reliable estimates of the numbers of actively transposing L1 elements are mostly nonexistent. While the human and mouse genomes contain comparable numbers of L1 elements, several phylogenetic and L1Xplore analyses in the mouse genome suggest that 1,500–3,000 active L1 elements currently exist and that they are still expanding in the genome. Conversely, the human genome contains only 150 active L1 elements. In addition, there is a discrepancy among the nature and number of mouse L1 elements in L1Xplore and the mouse genome browser at the UCSC and in the literature. To date, the reason why a high copy number of active L1 elements exist in the mouse genome but not in the human genome is unknown, as are the potential mechanisms that are responsible for transcriptional activation of mouse L1 elements. Methodology/Principal Findings: We analyzed the promoter sequences of the 1,501 potentially active mouse L1 elements retrieved from the GenBank and L1Xplore databases and evaluated their transcription factors binding sites and CpG content. To this end, we found that a substantial number of mouse L1